s observable
trait in the bodily behaviour that I am proposing to call "hunger,"
not some possibly mythical and certainly unknowable ingredient of the
animal's mind.

Generalizing what occurs in the case of hunger, we may say that what
we call a desire in an animal is always displayed in a cycle of actions
having certain fairly well marked characteristics. There is first a
state of activity, consisting, with qualifications to be mentioned
presently, of movements likely to have a certain result; these
movements, unless interrupted, continue until the result is achieved,
after which there is usually a period of comparative quiescence. A cycle
of actions of this sort has marks by which it is broadly distinguished
from the motions of dead matter. The most notable of these marks
are--(1) the appropriateness of the actions for the realization of a
certain result; (2) the continuance of action until that result has been
achieved. Neither of these can be pressed beyond a point. Either may
be (a) to some extent present in dead matter, and (b) to a considerable
extent absent in animals, while vegetable are intermediate, and display
only a much fainter form of the behaviour which leads us to attribute
desire to animals. (a) One might say rivers "desire" the sea water,
roughly speaking, remains in restless motion until it reaches either
the sea or a place from which it cannot issue without going uphill, and
therefore we might say that this is what it wishes while it is flowing.
We do not say so, because we can account for the behaviour of water by
the laws of physics; and if we knew more about animals, we might equally
cease to attribute desires to them, since we might find physical and
chemical reactions sufficient to account for their behaviour. (b) Many
of the movements of animals do not exhibit the characteristics of the
cycles which seem to embody desire. There are first of all the movements
which are "mechanical," such as slipping and falling, where ordinary
physical forces operate upon the animal's body almost as if it were
dead matter. An animal which falls over a cliff may make a number of
desperate struggles while it is in the air, but its centre of gravity
will move exactly as it would if the animal were dead. In this case, if
the animal is killed at the end of the fall, we have, at first sight,
just the characteristics of a cycle of actions embodying desire, namely,
restless movement until the ground is reached, and the